This invention relates to a method of treating a barrier metal surface prior to copper deposition thereon to improve the adhesion and trench filling characteristics of the copper deposition and, more particularly, to a method of pre-treating a barrier metal surface during a rapid thermal process in a vacuum or with a non-reactive gas such as hydrogen, argon or helium in a temperature range of 200 to 550 degrees Celsius, prior to the deposition of the copper film. The rapid thermal pre-treatment process improves the adhesion and trench filling characteristics of the subsequently deposited copper film.
Two of the challenges faced in the metallization process steps of integrated circuit (IC) fabrication include achieving good adhesion of a copper (Cu) film to the underlying barrier metal layer, and achieving good gap filling characteristics of the Cu film in narrow trenches or vias. In particular, it is difficult to fill narrow trenches or vias, having a diameter of 0.13 xcexcm or less, with copper (Cu) deposited by chemical vapor deposition (CVD), and at the same time maintain good adhesion of the Cu film to the underlying barrier metal film. Inadequate adhesion of the Cu film or uneven filling of the Cu film in the narrow trenches will result in an unusable or unreliable integrated circuit (IC) device.
In order to increase adhesion and gap filling characteristics of the Cu films, various pre-treatments and precursor compounds have been used. However, these pre-treatments and precursor compounds often result in variations in the deposited Cu film. These variations in the deposited Cu film are a severe problem which heretofore has hindered the application of CVD Cu films in IC processing.
The method of the present invention provides a rapid thermal process (RTP) wherein silicon wafers that are pre-coated with barrier metal films by either in-situ or ex-situ CVD or physical vapor deposition (PVD) are pre-treated, prior to deposition of a Cu film thereon, in a temperature range of between 300 and 550 degrees Celsius in a non-reactive gas such as hydrogen gas (H2), argon (Ar), or helium (He), or in an ambient vacuum. The chamber pressure typically is between 0.1 mTorr and 20 Torr, and the RTP time typically is between 30 to 100 seconds. Performing this rapid thermal process before the deposition of the Cu film results in a thin, shiny, densely nucleated, and adhesive Cu film deposited on a variety of barrier metal surfaces. The pre-treatment process eliminates variations in the deposited Cu film caused by Cu precursors. In other words, the RTP disclosed herein is insensitive to variation in precursor composition, volatility, and other precursor variables. Accordingly, the process disclosed herein is an enabling technology for the use of metal organic CVD (MOCVD) Cu in IC fabrication.
In particular, the invention comprises a method of pre-treating a barrier metal layer of a partially finished integrated circuit device prior to the deposition of a copper film thereon, comprising the steps of: providing a partially finished integrated circuit device including a barrier metal layer; subjecting said barrier metal layer to a temperature greater than 200 degrees Celsius for at least thirty seconds to form a pre-treated barrier metal layer; and depositing a copper film on said pre-treated barrier metal layer.
The invention further comprises a method of pre-treating a barrier metal layer of a partially finished integrated circuit device for the deposition of a copper film thereon, comprising the steps of: providing a partially finished integrated circuit device including a barrier metal layer having a trench or a via therein; subjecting said barrier metal layer to a temperature greater than 200 degrees Celsius for at least thirty seconds in an atmosphere chosen from the group consisting of: an ambient vacuum, hydrogen gas, argon gas, and helium gas to form a pre-treated barrier metal layer; and thereafter depositing a copper film on said pre-treated barrier metal layer and throughout said trench.
The invention also comprises an integrated circuit device manufactured by the process of: providing a partially finished integrated circuit device including a barrier metal layer; subjecting said barrier metal layer to a temperature greater than 200 degrees Celsius for at least thirty seconds; and thereafter depositing a copper film on said barrier metal layer.
Accordingly, an object of the invention is to provide a method of pre-treating a barrier metal layer so as to improve the deposition of a Cu film thereon.
A further object of the invention is to provide a method of pre-treating a barrier metal layer so as to improve the adhesion of a Cu film thereto.
Another object of the invention is to provide a method of pre-treating a barrier metal film so as to improve the trench and via filling characteristics of Cu applied thereto.
A further object of the invention is to provide a method of reducing variations in Cu deposition caused by Cu precursors.